A physician's knowledge wanes over time after training
That's generally accepted. There is a cerebral half life for many of the facts learned during training. The principle may not apply so much to knowledge in the physician's content area, which is reinforced by experience.
The process leads to better patient outcomes
There is weak evidence around this claim but it doesn't address cause and effect.
The public wants it
The statement is well supported by survey data but is it enough to justify the onerous and expensive process if evidence for real quality and outcome improvement is lacking?
An outsider (eg the specialty board) knows best the learning needs of the individual physician
A philosophical more than an evidential assumption, it's held up to ridicule by physicians “on the ground” while apparently holding sway with policy makers.
What does the evidence really say? Two reviews which address the question are noteworthy. This one from a couple of years ago was authored by officials of the ABIM and tends to be promotional although it cites much the same evidence noted in this recent and somewhat more objective review (related editorial here).
Here's the short version:
BC: Data on the correlation between BC status and patient outcomes are mixed. While some show a positive association the causality is unknown. It is equally likely that BC status and patient outcomes are linked by common factors inherent in the caliber of the physicians or their training programs.
MOC: The relationship to patient outcomes has not been specifically examined for MOC.
Processes of care
Both BC and MOC have been shown to correlate with performance metrics, but such metrics have not been validated as surrogates for quality or outcomes.
The more recent review has some interesting tidbits about participation in MOC. Participation among the leadership of internal medicine, even officials of the ABIM, was low! From the review:
We also calculated the recertification rate of the internal medicine leadership in various organizations using information collected from various websites in July 2009, which was approximately 20 years after the change in certification to a time-limited process. The initial ABIM task force on recertification has a recertification rate of 18% (3/17). The ABIM Board has a recertification rate of 20% (6/20). The editorial board for the Annals of Internal Medicine has a recertification rate of 9% (2/22). The ACP Governors have a recertification rate of 4% (2/54). The ACP Board of Regents has a recertification rate of 8% (2/26). The ACGME-RRC Internal Medicine Committee has a recertification rate of 0% (0/12). These are the statistics for internal medicine recertification only; the rates for recertification in subspecialty areas are slightly higher (Table 2). We repeated part of this analysis in June 2012. Twenty-six members of the ABIM board had lifetime certification, and six (23%) have voluntarily recertified. Thus, the participation by senior leadership in internal medicine has been unusually low; this seems surprising since many of these individuals promoted the initial process.
The editorial elaborates on this finding.